(1) Field of the Invention
The present invention relates to a thermal printer comprising a plurality of separately divided thermal heads each having a heater and a plurality of cassette ribbons incorporating each differently colored ink ribbon correspondingly to each thermal head and thermal printers for recording informations such as letters images, etc. on a printing medium by actuating selectively said heaters incorporated in a plurality of the thermal heads, more particularly to a multi-colored thermal printer for recording informations by arranging linearly 4 cassette ribbons incorporating 4 thermal heads and 4 cassette ribbons incorporating each independently 4 colored ribbon comprising black, cyan, magenta and yellow ribbons on a carriages in series to the conveying direction of recording medium.
(2) Description of the Prior Art
Conventional thermal printers have, in general, each a thermal head incorporating a plurality of heaters comprising thermally insulated semiconductors, etc. on a base board and the heaters are driven so as to heat said thermal heads by a certain information pattern and the thermal head is displaced after the completion of one print to print the subsequent information. Such a type issues low noise due to its absence of impact and characterized by a simple mechanism and low price, but since heat-sensitive paper should be employed as its recording medium, the running costs are higher.
There have been developed recorder which is free from impact by displacing ink ribbon prepared by coating lowmelting ink capable to be molten by heat in the form of film having a thickness of several microns to dozens microns on a substrate sandwiched between the recording medium and the thermal head relatively to the thermal head incorporating heater for heating said thermal head and which uses no heat-sensitive paper as the recording medium.
Under such a situation Published Japanese Patent Application No. 45969/1983 has proposed a multi-colored thermal printer comprising a plurality of thermal heads incorporating a plurality of separated heaters and a plurality of platens each corresponding to said plurality of separated heaters to feed the recording medium by the rotation of platens engaed frictionally with the recording medium and to convey successively the recording medium to each corresponding thermal head, said platens being driven by engaging frictionally against the outer peripheral surfaces of rotating rolls driven at a predetermined r.p.m. Further Published Japanese Patent Application No. 115279/1981 has proposed a multi-colored recorder of transference type which comprises plurality of ink layer-forming media installed spacedly each in a predetermined distance so as to be contacted with the recording medium conveyed through paper-feed rollers and recorder for transferring the image to the recording medium through a plurality of thermal heads. Furthermore, Published Japanese Patent Application Nos. 7390/1983 and 203084/1983 disclose color printers wherein one ink ribbon has a plurality of longitudinal color strips and at least one thermal head for each color is provided confrontedly to each color strip and the recording information is divided into each color to be fed to the corresponding thermal head(s).
Since conventional colored themal printer of serially transferring type have structures as indicated above, they have various disadvantages of complicated structure, high maintenance costs for exchanging the rink ribbons, high cost due to the large-sized printers, etc.
The printers as disclosed hereinbefore and claimed in Published Japanese Patent Application Nos. 7390/1983 and 203084/1983 have economical disadvantage that since the black, cyan, magenta and yellow inks are coated on the same ribbon, unnecessary colored strips are also conveyed together with the used colored strips to increase the running costs of ribbon.